Water Situation Report Solent and South Downs Area
Total Page:16
File Type:pdf, Size:1020Kb
Monthly water situation report Solent and South Downs Area Summary – May 2020 Solent and South Downs (SSD) had well below average rainfall for May, receiving 11% (6mm) of the long term average (LTA) (57mm). Monthly mean river flows across SSD ranged from exceptionally low to normal. End of month groundwater levels ranged from below normal to notably high. Soil moisture deficits across Solent and South Downs ended May much higher than LTAs. End of month reservoir stocks were above average at Ardingly Reservoir (Ouse Catchment) and Arlington Reservoir (Cuckmere catchment). Rainfall Solent and South Downs (SSD) had exceptionally low rainfall in across the entire area in May, receiving 11% (6mm) of the LTA (57mm). The Ouse areal unit in the east had the highest monthly total but still only 10mm, 18% of LTA (55mm), followed by neighbouring areal unit, Cuckmere, which had 17% (9mm) of LTA (52mm). The Lymington areal unit in the west of SSD received the lowest rainfall with 3mm (5% LTA), followed closely by the Test Chalk and Hampshire Tertiary areal units which both recorded 4mm (7% LTA). The highest daily totals for the month were recorded on the 23rd at World’s End (Hampshire Tertiaries) recording 12.2mm on one of only two days when it rained. On average, there was only one wet day over SSD, with 20 of the 68 rain gauges recording zero for the entire month. Soil Moisture Deficit/Recharge Soil moisture deficits across Solent and South Downs ended the month greater than the long term average; more than double for the Western Rother Greensand areal unit. Soils are much drier than normal. River Flows Monthly mean river flows across SSD ranged from notably low to above normal. The River Itchen at Allbrook & Highbridge was the only site recording above normal monthly mean flows, having the 3rd highest May monthly mean flow on record. The River Ouse at Goldbridge, the Adur at Sakeham and the Cuckmere at Cowbeech all recorded below normal monthly mean flows in May. Notably Low monthly mean flows were recorded for the Arun at Alfoldean and the Lymington at Brockenhurst, these rank as the 8th and 10th lowest May flows, respectively, on record. All other reported sites recorded normal flows. Groundwater Levels End of month groundwater levels ranged from below normal to notably high. Preston Candover and West Meon (East Hants Chalk) levels were notably high. Clanville Gate (Test Chalk), Cornish Farm (East Sussex Chalk) and Youngwoods Copse (Isle of Wight) levels were above normal. The only site below normal was Carisbrooke Castle (Isle of Wight) which is known to respond quickly. All other sites recorded normal groundwater levels in May. Observation boreholes Harting Common and Catherington were not dipped this month due to Covid-19 restrictions. The most notable levels this month were recorded at Preston Candover and West Meon Hut which were the 3rd and 4th highest end of May levels on record. Reservoir Storage/Water Resource Zone Stocks End of month reservoir stocks were above average at Ardingly Reservoir (Ouse Catchment) with 99.7% of total capacity (LTA 97%) and also above average at Arlington Reservoir (Cuckmere catchment) with 97% of total capacity (LTA 93%). Environmental Impact No water resources restrictions were in operation in May. No fluvial flood alerts or warning were issued in May. Author: HydrologySSD All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Environment Agency. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use of the information, or reliance upon views contained herein. www.gov.uk/environment-agency © Environment Agency 2020 Rainfall Map 1 Total rainfall for hydrological areas across Solent and South Downs for the current month, classed relative to an analysis of respective historic totals. Provisional data based on Environment Agency 1km gridded rainfall dataset derived from Environment Agency intensity rain gauges. Includes material based on Ordnance Survey 1:50 000 maps with the permission of the controller of Her Majesty’s Stationery Office © Crown copyright. All rights reserved. Environment Agency, 100026380, 2020. www.gov.uk/environment-agency © Environment Agency 2020 Rainfall Map 2 Total rainfall for hydrological areas across Solent and South Downs for the current month (up to 31 December), the last 3 months, the last 6 months, and the last 12 months, classed relative to an analysis of respective historic totals. Final NCIC (National Climate Information Centre) data based on the Met Office 5km gridded rainfall dataset derived from rain gauges (Source: Met Office © Crown Copyright, 2020). Provisional data based on Environment Agency 1km gridded rainfall dataset derived from Environment Agency intensity rain gauges. Crown copyright. All rights reserved. Environment Agency, 100026380, 2020 www.gov.uk/environment-agency © Environment Agency 2020 River Flow and Groundwater Status Map Underlined sites are observation wells not dipped owing to Covid-19 restrictions Groundwater site status based on end of month level. Surface water site status based on mean monthly flow. Some features of this map are based on digital spatial data licensed from the Centre for Ecology and Hydrology, © CEH. Includes material based on Ordnance Survey 1:50 000 maps with the permission of the controller of Her Majesty’s Stationery Office © Crown copyright. All rights reserved. Environment Agency, 100026380, 2020 Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC www.gov.uk/environment-agency © Environment Agency 2020 West Hampshire – Page 1 Monthly total rainfall (mm) Long term average rainfall (mm) Test Chalk - Rainfall Lymington - Rainfall 160 160 140 140 120 120 100 100 80 80 60 60 Rainfall (mm) Rainfall Rainfall (mm) Rainfall 40 40 20 20 0 0 Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Test Chalk - Effective Rainfall Lymington - Effective Rainfall 160 160 140 140 120 120 100 100 80 80 60 60 40 40 Effective (mm) Effective Rainfall (mm) Effective Rainfall 20 20 0 0 Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 RIVER TEST AT CHILBOLTON RIVER ITCHEN AT ALLBROOK GS AND HIGHBRIDGE Ranking used data from 09/01/1989 to 31/12/2017 Ranking used data from 01/10/1958 to 31/12/2017 16 14 14 12 12 10 10 8 8 6 6 4 4 Daily FlowMean (cumecs) Daily FlowMean (cumecs) Daily 2 2 0 0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 RIVER TEST AT BROADLANDS LYMINGTON RIVER AT BROCKENHURST Ranking used data from 01/10/1957 to 31/12/2017 Ranking used data from 01/01/1997 to 31/12/2017 35 30 30 25 25 20 20 15 15 10 10 Daily FlowMean (cumecs) Daily Daily FlowMean (cumecs) Daily 5 5 0 0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data www.gov.uk/environment-agency © Environment Agency 2020 West Hampshire – Page 2 CLANVILLE GATE GWL - CHALK PRESTON CANDOVER GWL - CHALK Ranking derived from data for the period Mar-1963 to Dec-2012 Ranking derived from data for the period Jan-1975 to Dec-2012 94 99 92 98 90 97 88 96 86 95 84 94 82 93 Level (mAOD) Level Level (mAOD) Level 80 92 78 91 76 90 74 89 Aug-19 Dec-19 Apr-20 Aug-19 Dec-19 Apr-20 WEST MEON GWL - CHALK LOPCOMBE CORNER GWL - CHALK Ranking derived from data for the period Sep-1986 to Dec-2012 Ranking derived from data for the period Apr-1963 to Dec-2012 94 98 92 96 94 90 92 88 90 86 88 84 86 84 82 Level (mAOD) Level Level (mAOD) Level 82 80 80 78 78 76 76 Aug-19 Dec-19 Apr-20 Aug-19 Dec-19 Apr-20 Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data www.gov.uk/environment-agency © Environment Agency 2020 East Hampshire and Isle of Wight Monthly total rainfall (mm) Long term average rainfall (mm) East Hampshire Chalk - Rainfall Isle of Wight - Rainfall 180 160 160 140 140 120 120 100 100 80 80 60 60 Rainfall (mm) Rainfall Rainfall (mm) Rainfall 40 40 20 20 0 0 Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 East Hampshire Chalk - Effective Rainfall Isle of Wight - Effective Rainfall 160 160 140 140 120 120 100 100 80 80 60 60 40 40 Effective (mm) Effective Rainfall (mm) Effective Rainfall 20 20 0 0 Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 RIVER WALLINGTON AT NORTH FAREHAM RIVER MEON AT MISLINGFORD Ranking used data from 01/01/1992 to 31/12/2017 Ranking used data from 01/10/1958 to 31/12/2017 12 6.0 10 5.0 8 4.0 6 3.0 4 2.0 Daily FlowMean (cumecs) Daily Daily FlowMean (cumecs) Daily 2 1.0 0 0.0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 RIVER MEDINA AT BLACKWATER Ranking used data from 01/05/1989 to 31/12/2017 2.5 2.0 1.5 1.0 0.5 Daily FlowMean (cumecs) Daily 0.0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 Exceptionally high Notably high Above normal Normal